If one's planning to resell to fund future upgrades, then scratches reduce value.
I don't resell so whatever price I pay is sunk costs. A more scratch resistant screen sounds nice but for the $800-1200 the SS/Ti with steel bands cost, I could upgrade 1-2 times already. I work in a mostly office setting so I'm willing to take my chances with the Ion-X display.
Maybe if/when I get my first major scratch on my aluminum S6, I'd reconsider the value proposition of models with sapphire crystal display. I don't mind micro scratches but deep obvious ones would annoy me. Titanium not stainless steel, though. I don't like heavy watches. I'd actually prefer something even smaller and lighter like the Fitbit Luxe but Fitbit doesn't natively sync to Apple Health.